/**
 * 时间复杂度：O(n^2)
 * @param {Number} matrix 
 * @returns 
 */
function sumMatrix(matrix) {
	let result = 0;
	for (let i = 0; i < matrix.length; i++) {
		for (let j = 0; j < matrix[i].length; j++) {
			result = result + matrix[i][j];
		}
	}
	return result;
}